1. Field of the Invention
The present invention relates to an image forming apparatus, a control method for the image forming apparatus, and a storage medium.
2. Description of the Related Art
Conventionally, image forming apparatuses are driven by power which is supplied from the outside of the apparatuses (i.e., power supplied from a commercial power source or a private electric generator).
Nowadays, in view of growing interest in global environmental issues and reducing running cost, various technologies which can contribute to saving energy are also developed for image forming apparatuses which use electrophotographic processes. According to some of these technologies, waste heat generated by the image forming apparatus or a component used in the apparatus is converted into electric energy and reused.
For example, in Japanese Patent Application Laid-Open No. 2008-052032 and Japanese Patent Application Laid-Open No. 2009-224684, techniques are discussed that convert heat dissipated from a fixing unit into power using a thermoelectric generating element arranged in the vicinity of the fixing unit.
The thermoelectric generating element uses a Seebeck element. The Seebeck element converts thermal energy directly into electrical power according to the Seebeck effect. When a temperature difference is caused to a thermoelectric conversion material including two different types of metals or a pair of a p-type semiconductor and an n-type semiconductor, a thermal electromotive force is produced at both junctions. It is distinguished characteristics that the Seebeck element does not require a driver such as a motor or a turbine and does not produce waste product.
Since the power generation of the Seebeck element is based on the temperature difference between a hot portion and a cold portion of one component (i.e., the opposite sides of one component), it is difficult to maintain the temperature difference and continue generating a predetermined power. This is because the heat is transmitted to the entire element,
Thus, Japanese Patent Application Laid-Open No. 2008-052032 and Japanese Patent Application Laid-Open No. 2009-224684 discuss a method which can maintain the temperature difference between the hot and the cold portions of a thermoelectric generating element and efficiently generate power.
According to Japanese Patent Application Laid-Open No. 2008-052032, while one side of a thermoelectric generating element is arranged in the vicinity of an outer wall of an image forming apparatus, the other side is arranged to contact a heat transfer unit. The heat transfer unit transfers the heat of the fixing unit to the thermoelectric generating element.
Further, according to Japanese Patent Application Laid-Open No. 2009-224684, a blocking unit is arranged on the heating side of the thermoelectric generating element. The blocking unit blocks the conduction of the heat generated by a heat generating body to the cold side but conducts the heat generated by the heat generating body to the heating side.
However, even if a thermoelectric generating element is configured such that the temperature difference between the hot and the cold portions is maintained and power is efficiently generated as described above, still, there are the problems described below.
For example, if a unit on the load side, which operates by the power to be generated, is a cooling fan which cools the inside of the enclosure of the image forming apparatus and, if a large electromotive force is necessary when the cooling unit is started, the cooling fan may not operate normally. This is because since the temperature difference (i.e., power generation amount) of the thermoelectric generating element is small when power is turned on, the electrical energy which has been generated may be too small for the normal operation of the cooling fan.